KR20140123780A - Photocured Coating Film, Polarizing Plate and Display Device - Google Patents

Abstract

The present invention provides a photo-curable coating film which has the maximum flexure load (Fmax) between 1.5 and 3.5 N, a polarizing plate including the coating film, and a display device thereof. The photo-curable coating film according to the present invention has excellent optical and mechanical properties as well as excellent properties regarding cracking due to bending and substrate fractures to be effectively used as a protective film or a polarizing plate.

Description

[0001] The present invention relates to a photocured coating film, a polarizing plate,

The present invention relates to a photo-curable coating film, a polarizing plate and a display device, and more particularly to a photo-curable coating film having excellent optical properties and mechanical properties, And a display device.

BACKGROUND ART [0002] Polarizing films used in image display devices such as a liquid crystal display, an electroluminescence (EL) display, a plasma display (PD), and a field emission display (FED) And a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin film. A protective film including triacetyl cellulose or the like is bonded to at least one surface of the polarizing film through an adhesive layer to make a polarizing plate, which is used for a liquid crystal display device or the like.

In order to improve the function of the polarizing plate, a coating film such as a hard coating film, a retardation film and an anti-reflection film may be included. Such a coating film should have high transparency, low haze, high hardness, good scratch resistance , And it is preferable that no crack occurs during the work or post-processing.

However, when an acrylic copolymer base material is used as a surface treatment base material, cracks due to bending of the film formed with the functional coating film and breaking of the base material occur. Such a problem is likely to occur during the roll to roll process in the production of the polarizing plate, and the yield of the polarizing plate is deteriorated due to cracking of the coating film and breakage of the substrate during handling of the polarizing plate.

Korean Patent No. 10-1127952 discloses a hard coating film for optical use which is excellent in optical and mechanical properties and has flexibility. The hard coating film is composed of a transparent plastic film or a substrate as a base layer, Acrylate monomers having two or more functional groups; At least one of a polyfunctional acrylate-based monomer and a polyfunctional urethane acrylate-based oligomer; And a hard coat layer for curing the UV curable resin composition comprising silica fine particles. However, the optical hard coat film has a problem in that the physical properties of the acrylic film substrate are deteriorated.

An object of the present invention is to provide a photocurable coating film having excellent optical and mechanical properties and excellent cracking and breaking property due to bending.

Another object of the present invention is to provide a polarizing plate provided with the coating film.

It is still another object of the present invention to provide a display device provided with the coating film.

On the other hand, the present invention provides a photocurable coating film having a maximum flexure load (Fmax) of 1.5 to 3.5 N.

In one embodiment of the present invention, the photocurable coating film has a coating layer formed on one side or both sides of the transparent substrate, including a cured product of the photocurable coating composition.

On the other hand, the present invention provides a polarizing plate provided with the coating film.

On the other hand, the present invention provides a display device provided with the coating film.

The photocurable coating film according to the present invention has a high transparency, a low haze, a high hardness and an excellent scratch resistance, as well as excellent cracking and breaking property due to bending, that is, bending resistance. Can be effectively used.

Hereinafter, the present invention will be described in more detail.

An embodiment of the present invention relates to a photocurable coating film having a maximum flexure load (Fmax) of 1.5 to 3.5 N.

In the present invention, the maximum flexural load refers to a load value at the time when the coating film is bent to cause cracking of the coating film and breaking of the substrate at the same time. The method for measuring the maximum flexural load of the coating film in the present invention is not particularly limited, and can be measured by, for example, the method described in Experimental Examples described later.

In one embodiment of the present invention, by adjusting the maximum flexural load of the photocurable coating film to a range of 1.5 to 3.5 N, the coating film exhibits cracking and substrate breaking characteristics due to excellent bending while maintaining excellent optical and mechanical properties .

In one embodiment of the present invention, the photocurable coating film has a coating layer formed on one side or both sides of the transparent substrate, including a cured product of the photocurable coating composition.

The composition of the photocurable coating composition used to prepare the photocurable coating film according to one embodiment of the present invention is not particularly limited as long as the coating film is formed so as to have a maximum flexural load of 1.5 to 3.5 N.

In one embodiment of the invention, the photocurable coating composition may comprise a photocurable (meth) acrylate oligomer and a monomer.

The photocurable (meth) acrylate oligomer may be at least one selected from the group consisting of epoxy (meth) acrylate, urethane (meth) acrylate and polyester (meth) Acrylate and a polyester (meth) acrylate may be used in combination.

The urethane (meth) acrylate can be prepared by reacting a compound having a polyfunctional (meth) acrylate having a hydroxyl group in the molecule and an isocyanate group in the presence of a catalyst according to a method known in the art. Specific examples of the polyfunctional (meth) acrylate having a hydroxyl group in the molecule include 2-hydroxyethyl (meth) acrylate, 2-hydroxyisopropyl (meth) acrylate, 4-hydroxybutyl (Metha) acrylate mixture, and a mixture of dipentaerythritol penta / hexa (meth) acrylate, a mixture of pentaerythritol tetra (meth) acrylate and caprolactone ring-opening hydroxyacrylate. Specific examples of the compound having an isocyanate group include 1,4-diisocyanatobutane, 1,6-diisocyanatohexane, 1,8-diisocyanatooctane, 1,12-diisocyanatododecane, Diisocyanato-2-methylpentane, trimethyl-1,6-diisocyanatohexane, 1,3-bis (isocyanatomethyl) cyclohexane, trans-1,4-cyclohexane diisocyanate, Diisocyanate, toluene-2,6-diisocyanate, xylene-1,4-diisocyanate, tetramethyl xylene-1, Diisocyanate, 1-chloromethyl-2,4-diisocyanate, 4,4'-methylenebis (2,6-dimethylphenyl isocyanate), 4,4'-oxybis (phenylisocyanate), hexamethylene diisocyanate And trifunctional isocyanate derived from trimethane propanol adduct toluene diisocyanate It may be at least one member selected from the group consisting of a carbonate.

The polyester (meth) acrylate can be prepared by reacting a polyester polyol and an acrylic acid according to methods known in the art. The polyester (meth) acrylate may be, for example, a polyester acrylate, a polyester diacrylate, a polyester tetraacrylate, a polyester hexaacrylate, a polyester pentaerythritol triacrylate, a polyester pentaerythritol tetraacryl And polyester pentaerythritol hexaacrylate, but is not limited to these.

The photocurable (meth) acrylate oligomer is preferably contained in an amount of 92 to 99 parts by weight based on 100 parts by weight of the solid content in the photocurable coating composition of the present invention. When the content of the oligomer is less than 92 parts by weight, cracking due to over-curing may occur. When the amount of the oligomer is more than 99 parts by weight, physical properties may be deteriorated due to uncured.

In one embodiment of the invention, the photocurable coating composition is a photocurable (meth) acrylate oligomer comprising a mixture of 2- to 5-functional polyester (meth) acrylate and 2- to 6-functional urethane (meth) .

The polyester (meth) acrylate is preferably contained in an amount of 20 to 50 parts by weight based on 100 parts by weight of the solid content in the photocurable coating composition. When the content of the polyester (meth) acrylate is less than 20 parts by weight, the cracking property is deteriorated. When the content is more than 50 parts by weight, mechanical property deterioration may occur.

The urethane (meth) acrylate is preferably contained in an amount of 45 to 85 parts by weight based on 100 parts by weight of solids in the photocurable coating composition of the present invention. When the content of the urethane (meth) acrylate is less than 45 parts by weight, the mechanical properties are deteriorated. When the content of the urethane (meth) acrylate is more than 85 parts by weight,

In one embodiment of the present invention, the monomer contained in the photocurable coating composition is a photocurable functional group which is used in the art having in its molecule an unsaturated group such as a (meth) acryloyl group, a vinyl group, a styryl group or an allyl group May be used without limitation, and specifically, a monomer having a (meth) acryloyl group can be used.

Examples of the monomer having a (meth) acryloyl group include neopentyl glycol acrylate, 1,6-hexanediol (meth) acrylate, propylene glycol di (meth) acrylate, triethylene glycol di Acrylate, trimethylolpropane tri (meth) acrylate, trimethylol ethane tri (meth) acrylate, triethylene glycol di (meth) acrylate, dipropylene glycol di (Meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, Acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate (Meth) acrylate, tripentaerythritol hexa (meth) acrylate, bis (2-hydroxyethyl) isocyanurate di (meth) acrylate, hydroxyethyl (Meth) acrylate, stearyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobutyl (meth) acrylate, , Phenoxyethyl (meth) acrylate, and isobonol (meth) acrylate, but are not limited thereto.

In particular, the use of the photo-curable monomer in the range of the content of the urethane (meth) acrylate in the mixture with the polyester (meth) acrylate can be used to increase the workability and compatibility of the photocurable coating composition , An equivalent level of cracking characteristics can be obtained.

In one embodiment of the invention, the photocurable coating composition may further comprise a photoinitiator and a solvent.

The photoinitiator can be used without limitation as long as it is used in the art. Specifically, the photoinitiator may be at least one selected from the group consisting of hydroxy ketones, aminoketones, and hydrogen recycling photoinitiators.

Examples of the photoinitiator include 2-methyl-1- [4- (methylthio) phenyl] 2-morpholinepropanone-1, diphenylketone, benzyldimethylketal, 2- 4-hydroxycyclophenyl ketone, 2,2-dimethoxy-2-phenyl-acetophenone, anthraquinone, fluorene, triphenylamine, carbazole, 3-methylacetophenone, 4- Quinolone acetophenone, 4,4-dimethoxyacetophenone, 4,4-diaminobenzophenone, 1-hydroxycyclohexyl phenyl ketone, benzophenone, and diphenyl (2,4,6-trimethylbenzoyl) phosphine Oxide, and the like.

It is preferable that the photoinitiator is included in an amount of 0.05 to 10 parts by weight based on 100 parts by weight of the photocurable coating composition of the present invention. If the amount of the photoinitiator is less than 0.05 part by weight, the curing speed of the composition is slow and uncured, resulting in poor mechanical properties. If the amount is more than 10 parts by weight, cracking may occur due to overaging.

The solvent is not particularly limited and can be used without limitation as long as it is used in the technical field. Specific examples thereof include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and diacetone alcohol, esters such as methyl formate, methyl acetate, ethyl acetate, ethyl lactate and butyl acetate, nitromethane, Nitrogen-containing compounds such as pyridine, pyrrolidone and N, N-dimethylformamide, ethers such as diisopropyl ether, tetrahydrofuran, dioxane and dioxolane, methylene chloride, chloroform, trichloroethane and tetrachloroethane Halogenated hydrocarbons, and other materials such as dimethyl sulfoxide, propylene carbonate, and 2-methoxyethanol. The solvents exemplified above may be used alone or in combination of two or more. More specifically, at least one selected from the group consisting of methyl acetate, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and 2-methoxyethanol may be used.

The solvent is preferably contained in an amount of 0.1 to 85 parts by weight based on 100 parts by weight of the photocurable coating composition of the present invention. If the content of the solvent is less than 0.1 parts by weight, the viscosity is high and the workability is poor. When the content of the solvent is more than 85 parts by weight, a long time is required in the drying and curing process.

In one embodiment of the invention, the photocurable coating composition may contain, in addition to the above components, components commonly used in the art such as antioxidants, UV absorbers, light stabilizers, thermal < , A surfactant, a lubricant, an antifouling agent, and the like.

As the transparent substrate used in the photocurable coating film according to the embodiment of the present invention, any plastic film having transparency can be used. For example, cycloolefin-based derivatives having units of monomers including cycloolefins such as norbornene and polycyclic norbornene monomers, cellulose (such as diacetylcellulose, triacetylcellulose, acetylcellulose butylate, isobutylestercellulose, Propylene cellulose, butyryl cellulose and acetyl propionyl cellulose), ethylene vinyl acetate copolymer, polyester, polystyrene, polyamide, polyether imide, polyacryl, polyimide, polyether sulfone, polysulfone, polyethylene, polypropylene, Polyolefins such as polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, polyethersulfone, polymethylmethacrylate, polyethylene terephthalate, polybutylene terephthalate, Polyethylene naphthalate Polyesters, polycarbonates, polyurethanes, and epoxies. Unstretched, uniaxially or biaxially stretched films can be used.

Specifically, among the above-mentioned transparent materials, monoaxially or biaxially stretched polyester films excellent in transparency and heat resistance, cycloolefin-based derivative films excellent in transparency and heat resistance, capable of coping with the enlargement of the film, transparent and optically anisotropic A triacetylcellulose film having no transparency and a low-cost acrylic copolymer film can be suitably used. More specifically, an acrylic copolymer film with high transparency and low cost can be used in accordance with recent market demands.

The thickness of the transparent substrate is not particularly limited, but may be 8 to 1000 탆, specifically 20 to 150 탆. If the thickness of the transparent base material is less than 8 占 퐉, the strength of the film is lowered and the workability is lowered. If the thickness is more than 1000 占 퐉, the transparency is lowered or the weight of the polarizing plate is increased.

A coating film according to an embodiment of the present invention can be produced by applying the above-mentioned photocurable coating composition on one side or both sides of a transparent substrate and curing to form a coating layer.

The photocurable coating composition can be coated on a transparent substrate by appropriately using known methods such as die coater, air knife, reverse roll, spray, blade, casting, gravure, microgravure, spin coating and the like.

After the photocurable coating composition is applied to the transparent substrate, the volatiles are evaporated to dryness at a temperature of 30 to 150 DEG C for 10 seconds to 1 hour, more specifically 30 seconds to 30 minutes, Irradiation and curing. The irradiation amount of the UV light may be about 0.01 to 10 J / cm 2, and more specifically, about 0.1 to 2 J / cm 2.

In this case, the thickness of the formed coating layer may be specifically 2 to 30 탆, more specifically 3 to 15 탆. When the thickness of the coating layer is within the above range, an excellent hardness effect can be obtained.

One embodiment of the present invention relates to a polarizing plate provided with the above-mentioned coating film. A polarizing plate according to an embodiment of the present invention can be produced by laminating the above-mentioned coating film on at least one surface of a polarizing film.

The polarizing film is not particularly limited. For example, a polarizing film such as a polyvinyl alcohol film, a partial saponification film of ethylene-vinyl acetate copolymerization system, or the like may be produced by adsorbing a dichromatic substance such as iodine or a dichromatic dye onto a single- A stretched film, a dehydrated product of polyvinyl alcohol, a dehydrochlorinated product of polyvinyl chloride, and the like can be used. Specifically, a film made of a dichromatic material such as a polyvinyl alcohol-based film and iodine can be used. The thickness of these polarizing films is not particularly limited, but is generally about 5 to 80 占 퐉.

One embodiment of the present invention relates to a display device provided with the above-mentioned coating film. For example, by incorporating the polarizing plate having the coating film of the present invention in a display device, it is possible to manufacture various display devices having excellent visibility. In addition, the coating film of the present invention may be attached to a window of a display device.

The coating film according to one embodiment of the present invention can be used in reflective, transmissive, semi-transmissive LCD or various driving LCDs of TN type, STN type, OCB type, HAN type, VA type and IPS type. The coating film according to an embodiment of the present invention can also be used in various display devices such as a plasma display, a field emission display, an organic EL display, an inorganic EL display, and an electronic paper.

Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples and Experimental Examples. It should be apparent to those skilled in the art that these examples, comparative examples and experimental examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Examples 1 to 4 and Comparative Examples 1 to 5: Preparation of photocurable coating film

The photocurable coating compositions were prepared by mixing the respective components in the proportions (unit: wt%) as shown in Table 1 below.

urethane
Acrylate Polyester
Acrylate Monomer solvent Photoinitiator additive 6 sensation Four-sensory Trifunctional Example 1 4.8 8 27.2 57.7 2.0 0.3 Example 2 4.2 12 23.8 57.7 2.0 0.3 Example 3 3.6 16 20.4 57.7 2.0 0.3 Example 4 3 20 17 57.7 2.0 0.3 Comparative Example 1 5.4 4 30.6 57.7 2.0 0.3 Comparative Example 2 2.4 24 13.6 57.7 2.0 0.3 Comparative Example 3 40 57.7 2.0 0.3 Comparative Example 4 40 57.7 2.0 0.3 Comparative Example 5 40 57.7 2.0 0.3

The components used in Table 1 are as follows.

Urethane acrylate: urethane hexaacrylate (PU610)

Polyester acrylate: Polyester tetraacrylate (PS420)

Monomer: Pentaerythritol triacrylate (M340)

Solvent: methyl ethyl ketone, 2-methoxyethanol

Photoinitiator: 1-hydroxycyclohexyl phenyl ketone

Additive: Modified silicone polymer (BYK-3530)

Each of the photocurable coating compositions prepared as described above was stirred for 1 hour and then coated on a transparent base film (80 mu m, PMMA) with a Meyer bar (a kind of gravure coater) so as to have a thickness of 6 mu m. For 1 minute, and then cured at 500 mJ / cm < ² > to prepare a coating film.

Experimental Example 1:

The coating films prepared in the above Examples and Comparative Examples were evaluated as follows. The results are shown in Table 2 below.

(1) Total light transmittance

The total transmittance and total haze of the PMMA surface were measured using a spectrophotometer (HZ-1, manufactured by Nippon Sugar Co., Ltd.) toward the light source (D65).

(2) Pencil hardness

The surface of the prepared coating film was subjected to a 500 g load with a pencil hardness tester (PHT, Korea Science and Engineering) and the pencil hardness was measured. The pencil was made five times per pencil hardness using Mitsubishi products. If the number of cigarettes is two or more, it is judged to be defective, and the pencil hardness is indicated by a pencil before the defective.

Kiss 0: OK

Kiss 1: OK

Gas 2 or higher: NG

(3) scratch resistance

Scratch resistance was tested by reciprocating 10 times under 1 kg / (2 cm x 2 cm) using a steel wool tester (WT-LCM100, Korea Protec Co.). Steel wool used # 0000.

A: 0 scratches

A ': 1 to 10 scratches

B: 11-20 scratches

C: 21 ~ 30 scratches

D: More than 31 scratches

(4) Adhesion

11 straight lines were drawn on the coated side of the film at intervals of 1 mm to form 100 squares, and then peel test was performed three times using a tape (CT-24, Nichii Co., Ltd.). Three 100 squares were tested and the average was recorded. The adhesion was recorded as follows.

Adhesion = n / 100

n: Number of rectangles that are not to be peeled off

100: total number of squares

Therefore, when one of them was not peeled off, it was recorded as 100/100.

(5) Flexibility

The manufactured coating film was subjected to a bending test using a plate-to-plate jig in a flexure mode using a universal testing machine (Universal Testing Machine 5567, Instron), and the maximum flexure load (Fmax ) Were measured.

The sample size was 20 mm x 40 mm (width x length), and the plate-to-plate spacing was kept at 35 mm. Both ends of the sample were fixed at 20 mm from the center of each plate. At this time, the slightly curved film reference coating film was directed to the outside. The bending test was carried out at a speed of 20 mm / min. The film was flexed to reduce the curvature of the film with time, and the Fmax value at which the cracking of the coating film and the breakage of the substrate occurred simultaneously was recorded.

division Total light transmittance
(%) Hayes
(%) Pencil hardness
(H) Scratch resistance Adhesiveness Flexibility
Fmax (N) Example 1 91.9 0.3 2 A ' 100/100 1.589 Example 2 91.8 0.3 2 A ' 100/100 2.431 Example 3 91.8 0.3 2 A ' 100/100 2.874 Example 4 91.9 0.3 2 A ' 100/100 3.541 Comparative Example 1 91.8 0.3 2 A ' 100/100 1.052 Comparative Example 2 91.8 0.3 2 B 100/100 4.101 Comparative Example 3 91.8 0.3 2 A 100/100 0.882 Comparative Example 4 91.8 0.3 One D 100/100 4.875 Comparative Example 5 91.8 0.3 2 A 100/100 0.785

As shown in Table 2, the photocurable coating films of Examples 1 to 4 of the present invention exhibited excellent flexing resistance while maintaining optical and mechanical properties.

On the other hand, in the case of Comparative Examples 1 to 5, it was confirmed that the mechanical strength and bending resistance were lowered.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Do. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Accordingly, the actual scope of the invention is defined by the appended claims and their equivalents.

Claims (14)

A photocurable coating film having a maximum flexure load (Fmax) of 1.5 to 3.5 N. The photocurable coating film according to claim 1, wherein a coating layer comprising a cured product of the photocurable coating composition is formed on one side or both sides of the transparent substrate. The photocurable coating film of claim 2, wherein the photocurable coating composition comprises a photocurable (meth) acrylate oligomer and a monomer. The photocurable coating film according to claim 3, wherein the photocurable (meth) acrylate oligomer is a mixture of urethane (meth) acrylate and polyester (meth) acrylate. The photocurable coating film according to claim 3, wherein the photocurable (meth) acrylate oligomer is contained in an amount of 92 to 99 parts by weight based on 100 parts by weight of solids in the photocurable coating composition. The photocurable coating film according to claim 3, wherein the photocurable (meth) acrylate oligomer is a mixture of 2 to 5 functional polyester (meth) acrylate and 4 to 6 functional urethane (meth) acrylate. The photocurable coating composition according to claim 6, wherein 20 to 50 parts by weight of polyester (meth) acrylate and 45 to 85 parts by weight of urethane (meth) acrylate are contained relative to 100 parts by weight of solids in the photocurable coating composition Photocurable coating film features. The photocurable coating film according to claim 3, wherein the monomer is a monomer having a (meth) acryloyl group. The photocurable coating composition according to claim 7, wherein a part of the 4 to 6-functional urethane (meth) acrylate in the mixture is replaced with a photocurable monomer. The photocurable coating film of claim 3, wherein the photocurable coating composition further comprises a photoinitiator and a solvent. The photocurable coating film according to claim 10, wherein 0.05 to 10 parts by weight of a photoinitiator is contained and 0.1 to 85 parts by weight of a solvent is contained per 100 parts by weight of the photocurable coating composition. The photocurable coating film according to claim 2, wherein the transparent base material is an acrylic copolymer film. A polarizing plate comprising the coating film according to claim 12. A display device comprising the coating film according to claim 12.